class FieldPresenceEnhancer

FieldPresenceEnhancerTest.php in drupal/core/vendor/symfony-cmf/routing/Symfony/Cmf/Component/Routing/Tests/Enhancer/FieldPresenceEnhancerTest.php

class FieldPresenceEnhancer implements RouteEnhancerInterface {

  /**
   * @var string field for the source class
   */
  protected $source;

  /**
   * @var string field to write hashmap lookup result into
   */
  protected $target;

  /**
   * value to set the target field to
   *
   * @var string
   */
  private $value;

  /**
   * @param string $source the field name of the class
   * @param string $target the field name to set from the map
   * @param string $value  value to set target field to if source field exists
   */
  public function __construct($source, $target, $value) {
    $this->source = $source;
    $this->target = $target;
    $this->value = $value;
  }

  /**
   * {@inheritDoc}
   */
  public function enhance(array $defaults, Request $request) {
    if (isset($defaults[$this->target])) {

      // no need to do anything
      return $defaults;
    }
    if (!isset($defaults[$this->source])) {
      return $defaults;
    }
    $defaults[$this->target] = $this->value;
    return $defaults;
  }

}